Gåden er løst! Det var Grundtvigs Højskole i Lyngby i sommeren 1916. Min bedstemor var student der dengang. Oplysningen kom fra Grundtvigs Højskole via Højskolebladet.
The Mystery has been solved! It was Grundtvig's Folk High School in Lyngby in the summer of 1916. My grandmother was a student there then. The answer came from Grundtvig's High School via the folk high school magazine.